Geological origin of Bitumen

Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae and other once-living things. When these organisms died, their remains were deposited in the mud on the bottom of the ocean or lake where they lived. Under the heat and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum. Deposits at the La Brea Tar Pits are an example.

There are structural similarities between bitumen and the organic matter in carbonaceous meteorites. However, detailed studies have shown these materials

to be distinct.
Given that analogous matter is found in certain meteorites and bitumen are also found in Archean rocks it is possible that some bitumen are primordial material formed during accretion of the Earth and reworked by bacteria that consume hydrocarbons.